I have the series
$$\sum_{k=1}^{\infty}\frac{z^k}{ak + 1}$$
and am wondering whether it relates to any function that any of you knows?
The most similar that I know is the series representation of a polylogarithm of order $s$ is given by
$$\text{Li}_s(z) = \sum_{k=1}^{\infty}\frac{z^k}{k^s}$$
with $s=1$ but I cannot find anything closer.
The series (starting at $k=0$) is $a^{-1} \Phi(z, 1, 1/a)$ where $\Phi$ is the Lerch Phi function.